This is my first post so be gentile please.
1. First of all get an Affliction Warlock (you need to be the one playing the Warlock) and head to any sort of raid testing dummies such as the ones in Shrine.
2. Duel the other player once it starts the Affliction Warlock must fully dot up the raid dummy.
3. Once fully dotted (and snapshotted if you care for the optimal damage to ensure they die) soulswap them to the player.
Even if you lose or win the duel, they will die if the dots persist past their minimum health and they will die.
Hope you Warlocks have fun with this one!
Sorry I don't have any video or screenshots I just wanted to add it quickly. May upload some very soon.